This invention relates to a method of restoring a wire electrode employed in a wire electrode-type electric discharge machine, and to the apparatus for effecting such restoration, and more particularly to a method and apparatus for restoring a wire electrode which permits an electric discharge machining operation to be resumed automatically in a short period of time in the event of wire electrode breakage.
An electric discharge machine which uses a wire electrode as a cutter establishes a voltage differential between the electrode and a workpiece to induce an electric discharge or spark in the intervening space. The machine moves the workpiece relative to the wire electrode on the basis of data representative of machining instructions, thereby allowing the workpiece to be machined into a desired shape owing to the action of the electric discharge. There are occasions where the electrode breaks within the workpiece during the machining operation if such machining conditions as the applied voltage and feed speed are improper. In such an event, the operator must repair the broken electrode first by removing the broken portion from a take-up mechanism side, pulling the electrode upwardly through a lower guide from a supply mechanism, passing the end of the electrode through the slot which has been machined in the workpiece, and then fastening it to the take-up mechanism after passing it through an upper guide. Restoring the wire electrode in this manner so that machining can resume from the former position requires a considerable amount of time, particularly for threading the wire through the upper and lower guides, and results in diminished machining efficiency. Moreover, since the intervention of the operator is necessary to repair the broken wire electrode, the discharge machining operation will not be able to resume if the wire should break during unattended operation.